1. Field of the Invention
The present invention relates to a transflective type liquid crystal display device, and more particularly to a transflective thin film transistor substrate and a fabricating method thereof that simplifies the fabrication process, and a liquid crystal display panel using the same and a fabricating method thereof.
2. Description of the Related Art
A liquid crystal display device controls the light transmittance of a liquid crystal that has dielectric anisotropy by use of an electric field, thereby displaying a picture. The liquid crystal display device includes a liquid crystal display panel for displaying a picture through a liquid crystal cell matrix and a drive circuit for driving the liquid crystal display panel.
Referring to FIG. 1, a liquid crystal display panel of the related art includes a color filter substrate 10 and a thin film transistor substrate 20 that are bonded together with a liquid crystal 24 therebetween.
The color filter substrate 10 includes a black matrix 4, a color filter 6, and a common electrode 8 that are sequentially formed on an upper glass substrate 2. The black matrix 4 is formed in a matrix shape on the upper glass substrate 2. The black matrix 4 divides an area of the upper glass substrate 2 into a plurality of cell areas where the color filters are to be formed, and the black matrix 4 prevents light interference between adjacent cells and an external light reflection. The color filter 6 is divided into red R, green G, and blue B in the cell areas divided by the black matrix 4. The common electrode 8 formed of a transparent conductive layer on the entire surface of the color filter 6 supplies a common voltage Vcom or a reference voltage when driving a liquid crystal 24. Also, an overcoat layer (not shown) might be further formed between the color filter 6 and the common electrode 8 to level the color filter 6.
The thin film transistor substrate 20 includes a thin film transistor 18 and a pixel electrode 22 that are formed at each cell area defined by the crossing of a gate line 14 and a data line 16 on a lower glass substrate 12. The thin film transistor 18 supplies a data signal from the data line 16 to the pixel electrode 22 in response to a gate signal of the gate line 14. The pixel electrode 22 formed of the transparent conductive layer supplies the data signal from the thin film transistor 18 to drive the liquid crystal 24.
The liquid crystal 24 having dielectric anisotropy controls a light transmittance by rotating in accordance with an electric field formed by the data signal on the pixel electrode 22 and the common voltage Vcom on the common electrode 8.
The liquid crystal display panel further includes a spacer (not shown) for uniformly maintaining a cell gap between the color filter substrate 10 and the thin film transistor substrate 20. A ball spacer or column spacer may be used as the spacer.
The color filter substrate 10 and the thin film transistor substrate 20 of the liquid crystal display panel are formed using a plurality of mask processes. One mask process includes many processes such as thin film depositing (coating), cleaning, photolithography, etching, photo-resist stripping, inspecting, etc. Specifically, the thin film transistor substrate is manufactured using a semiconductor process and requires a plurality of mask processes, thus its fabricating process is complicated is a major contributor to the manufacturing cost of the liquid crystal display panel.
Further, the liquid crystal display panels are divided into three different types: a transmission type that displays a picture by use of a light incident from a backlight unit; a reflection type that displays a picture by reflecting an external light such as a natural light; and a transflective type that combines the transmission type and the reflection type.
There is a problem in that the transmission type display consumes too much power due to the backlight unit and the reflection type display cannot display a picture in a dark environment because the reflection type depends on the external light. But the transflective type display operates in a reflection mode if the external light is sufficient and in a transmission mode using the backlight unit if the external light is not sufficient, thus the electric power consumption may be reduced versus than in the transmission type display and the transflective type display is not dependent on external light like the reflection type.
To this end, the transflective type liquid crystal display panel has each pixel divided into a reflection area and a transmission area. Accordingly, the transflective thin film transistor substrate should further include a reflection electrode formed in the reflection area, and an organic insulating film formed to be relatively thick under the reflection electrode in order to equalize a light path length of the reflection area to that of the transmission area. As a result, the related art transflective thin film transistor substrate has a problem in that its fabricating process is complicated because of the number of mask processes.
Further, the related art transflective thin film transistor substrate has a transmission hole that penetrates a thick insulating film in the transmission area, thus light leakage is generated by a rubbing defect caused by a step difference between the reflection area and the transmission area. As a result, the contrast ratio is decreased.
In addition, the related art transflective thin film transistor substrate has the reflection electrode overlap the data line in order to prevent light leakage at both sides of the data line. Because of this, a parasitic capacitance is generated between the reflection electrode and the data line that causes problems such as vertical cross talk, power consumption increase, etc.